Not Applicable.
This invention relates in general to bearings and more particularly to a rotary fluid bearing and a process for manufacturing the same.
The typical fluid bearing includes a journal and a hub, one of which rotates with respect to the other. Sometimes a small electric motor is integrated into the journal and hub to effect the rotation. The journal and hub have matching surfaces which, during the operation of the bearing, are separated by a thin layer of fluid. In this sense, a fluid may comprise any material, such as a liquid or gas that possesses fluid properties or characteristics. Hence, the surfaces do not contact each other and essentially no friction exists to impede the rotation. The fluid for the layer, and the pressure associated with the fluid, may come from an external source (hydrostatic) or it may derive from the rotation itself (hydrodynamic). Bearings which operate on the latter principle normally have grooves in the surfaces of the journal or hub to elevate the fluid pressure in the gap between opposed thrust-oriented surfaces. Such bearings are referred to as self-acting bearings.
However, the journal and hub in a self-acting bearing contact one another when the bearing is not rotating or otherwise not in use. Each time the bearing activates, the hub and journal surfaces that are in contact rub against one another during initial rotation, that is, before sufficient fluid pressure separates the surfaces. The journal and hub surfaces thereby suffer scuffing and wear, which leads to inefficiency and premature failure. If one of the bearing members has an epoxy or resin liner that chemically reacts with the metal of the opposing bearing member, such as aluminum or steel, physical contact between the members intensifies the inefficiencies and accelerates premature failure.
Further, in certain configurations the self-acting fluid bearing has its opposed thrust-oriented surfaces tapered, indeed, down from each end toward the mid-region of the bearing. The tapers, in effect, capture the hub on the journal, but this presents manufacturing problems. In this regard, the tapered regions of the journal are normally manufactured separately and then assembled within the hub. Since the two tapered regions are not machined on the same center, the possibility exists that their axes may not coincide precisely as they must when assembled in the hub. This can produce error in motion. In addition, the surfaces conjoining between the two tapered regions must be manufactured so as to prevent any slippage at the interface during bearing rotation.
The present invention resides in the formulation for, and process of applying, a coating on one or more of the internal members of the bearing that has a lower coefficient of friction and lower chemical reactivity than the material it coats, and in the xe2x80x9ccoiningxe2x80x9d of features on the abutting end faces of two separable sections of the internal bearing member.
The present invention greatly reduces the scuffing and wear associated with starting and stopping the bearing, and eliminates the chemical reaction between the liner and opposing metal bearing components, through the application of a specially formulated and applied coating on one or more of the internal members of the bearing. The coating may also be formulated to increase the hardness of the substance it coats.
The present invention also resides in xe2x80x9ccoiningxe2x80x9d features onto the surfaces of the tapered sections abutting one another that thereafter properly mate with one another in only one position. The present invention provides an alignment mechanism that also eliminates lateral slippage of the sections when they are conjoined. In this way, the sections can be quickly, reliably and repeatably aligned together properly to enable multiple manufacturing steps that separate and rejoin the sections, including final bearing assembly.